Question

Why is winter colder than summer?

Answer 1

In winter the earth's axis is tilted away from the sun causing the sun's rays to be spread over a more oblique area than in the summer.

Explanation:

As (hopefully) can be seen in the diagram below, a fixed width band of the sun's rays shining on equidistant points from the equator is spread over a much wider area in the hemisphere where the axis is pointing away from the sun.

Note that if you live in the Northern hemisphere, you are actually closer to the sun in the winter than in the summer.